A rotary evaporator is a piece of laboratory equipment which includes a heating bath and an evaporator flask which can dip into the heating bath. In operation, a liquid medium present in the heating bath, for example water or—for higher temperatures—oil, is heated in order thus to heat the evaporator flask dipped into the heating bath. A liquid mixture contained in the evaporator flask can hereby be heated so that the respective distillate, in particular solvent, is evaporated. The evaporated distillate then flows into a cooler of the rotary evaporator to condense there. The condensate is subsequently collected in a collection flask. The distillation residue remaining in the evaporator flask can be further processed or analyzed. A vacuum pump is frequently additionally provided for the generation of a vacuum in the evaporator flask and in the cooler to lower the boiling point, whereby the distillation can be accelerated and the distillation rate can be increased.
A rotary evaporator furthermore includes a rotary drive for the rotation of the evaporator flask in the heating bath. The evaporator flask is uniformly heated due to the rotation and a thin liquid film, which has a large surface and from which the distillate can be evaporated fast, efficiently and gently, is produced at the heated inner wall of the evaporator flask.
In order to set the rotary damper into rotation which is, for example, rotationally fixedly connected to the initially named steam leadthrough via a ground joint, the steam leadthrough, which is formed as a hollow glass shaft and which serves to conduct the evaporated distillate from the evaporator flask to the cooler, is rotatingly driven by the rotary drive. Such a ground joint is usually secured using a Keck clamp. To enable the rotary drive of the steam leadthrough, a clamping insert having a sleeve-like basic shape can be arranged between a rotatingly drivable hub of the rotary drive and the steam leadthrough, said clamping insert clamping the steam leadthrough in a force-transmitting manner in the hub.
The steam leadthrough is connected at the cooler side to a cooler connection of the cooler, with a seal, in particular a sealing ring, being provided fixed to the housing between the cooler connection of the stationary cooler and the end of the rotatable steam leadthrough at the cooler-side end. Such a seal has, however, only a limited operating life.